I messaged @soren about adding support for solenoid 03A (Ball Popper) and 15 (sling kicker) and didn't hear back. I asked a similar question in the Radical Club thread about adding his mods to the proto rom and he said no.

Here's what I see with the proto roms.

When the fork switch is closed
1) run the Snake Run Bonus award sequence
2) fire 2 flash lamps. (The ones on either side of the crossover ramp diverter)
3) fire solenoid 03A (the ball should land on and stay on the plastic ramp)

I had to reduce the coil strength in order to keep the ball from bouncing off the ramp most of the time.

It is the same switch (in the matrix), 16, that starts the sequence. The physical switch is different and the software must treat it differently.

I presented the question from both directions just to see if I could start a dialog. He's probably limited by the lack of a prototype game to test on. And then there's the issue of the tiny target audience, unless it's configurable. I'd be interested in understanding how he creates his mods. Does he have source? What's the build environment, etc.

Does anybody know Dan Lee?

When I first installed the proto ROMs I was able to get the extra slingshot working using switch 49, which is not used on production models. A sling sound effect is played. However, I was not able to activate the bonus sequence by hitting the spot target used on the production games. IIRC, I had to hold it closed to start the bonus sequence. Once I installed the popper and fork switch it worked fine. Comparing the spot target (momentary) to the fork switch (which remains closed), it seemed that the software must use different routines.

The vuk moves the ball from under the playfield to the ramp. The vuk is served by a ramp under the playfield and a gobble hole allows the ball to reach that ramp. Production models have the spot target (switch 16) mounted forward in the gobble hole, blocking access to the hole. On the protos the hole is open and the switch is a fork switch (using switch 16) mounted to the vuk assembly. The hole (or the spot target on production models) is not always accessible. It is mostly blocked by a 3 bank drop target assembly that resets shortly after all three targets are dropped. Since all that the vuk does is move the ball to the ramp it is not missed much on the production models. It slows the game down because it waits for the bonus sequence to complete before putting the ball back into play.